Atsuko Mori

Seasonal variation in atmospheric aerosols concentration covering northern Kyushu, Japan and Seoul, Korea

Abstract Atmospheric aerosols were collected from October 1990 to February 1992 in northern Kyushu (Tsushima and Ogori), Japan and Seoul, Korea, simultaneously using identical sampling system and chemical analysis methods. Observed data were analyzed with meteorological data to clarify the seasonal variations in aerosol concentration and composition. Dominant ion components of aerosol were SO42− in anion and NH4+ in cation. The concentrations of ion components were higher in winter than those in summer. Equivalent concentration ratio of particulate nitrate and sulfate ( NO 3 − SO 4 2− ) showed high value in Ogori having a peak in winter season. Equivalent concentration ratio of Ca2+ and sulfate ( Ca 2+ SO 4 2− ) is highest in Seoul and shows no seasonal variation. On the contrary, Tsushima and Ogori showed low value in summer season. In summer, this area is affected by the atmospheric high-pressure system which developed at the southern Kyushu sea area and southerly monsoon wind predominate. As the result of this, supply of Ca2+ from soil should be diminished in summer. Equivalent concentration ratio of particulate Cl− and Na+ ( Cl − Na + ) in August was half compared with the ratio observed in February. Episode analysis of June 1991 and February 1992 indicated the transportation of pollutants from the outside of Japan. Air masses from the Chinese continent have been concluded to bring the greatest amount of anthropogenic pollutants to Korea and Japan.

Precipitation chemistry in Japan 1989–1993

Precipitation chemistry in Japan was discussed on a wet-only sample database obtained in a nationwide survey from April 1989 to March 1993. Wet-only samples were collected at 29 stations over Japan on a biweekly basis. Commonly determined chemical parameters were measured in laboratories. The volume-weighted annual mean pH at each site ranged from 4.50 to 5.83 with a mean of 4.76. Concentration ranges and means (parenthesized) on an equivalent basis for major ions were as follows: nss-SO42−; 5.2–58.9 (38.6), NO3−; 1.8–25.0 (14.1), NH4+; 0.55–29.8 (18.3), nss-Ca2+; 2.0–34.5(14.2), Na+; 6.4–275.3 (49.1), Cl−; 13.7–322.4 (63.5) β eq L−1. Acid-base relationships for Phase-II records were quantitatively discussed in terms of three measures: pH, fractional acidity, and our proposed pAi.

High sulfate and nitrate concentrations in precipitation at Nagasaki impacted by long-distant and local sources

Abstract Wet-only event-basis precipitation data at Nagasaki, the border area between the Asian Continent and Japan, with high non-sea-salt (nss-) SO 2- 4 and NO - 3 concentrations from November 1983 through March 1988 were analyzed in terms of wind conditions at upper and surface levels to assess both long-distant and local sources. In order to investigate the high nss-SO 2- 4 concentration events occurring with similar transport patterns, the wind conditions were grouped into the following three types: type 1, the upper air flow from the Asian Continent and the surface wind from the sea; type 2, the stagnant upper air and the surface wind from the land at and around Nagasaki; and type 3, the upper air flow from the Continent and the surface wind from the land. In the case of high NO - 3 concentration events, their wind-condition types were similar to those for high nss-SO 2- 4 concentration events. These three types for both ions were discussed to estimate their sources as follows: type 1, long-distant sources in the Asian Continent; type 2, local sources at and around Nagasaki; and type 3, both long-distant and local sources. From the viewpoint of precipitation chemistry, the ratios of H + /(nss-SO 2- 4 +NO - 3 ) were evaluated for the high concentration events so as to examine the degree of neutralization of acidic input, H 2 SO 4 and HNO 3 . High ratios events corresponded to wind-condition type 2 whereas low ratios were associated with types 1. This suggested that the acidic input from local sources were little neutralized to cause much higher acidity in precipitation than those from long-distant sources.

Relationship between wet deposition of sulfate and nitrate and rainfall amount in Japan

A regression model of wet deposition on rainfall amount for non-seasalt sulfate (nss-SO42−) and nitrate (NO3−) was applied to a data set obtained through a nationwide survey from April 1989 to March 1993. Wet-only samples on a biweekly basis were collected at 29 sites over Japan. Reparameterized bivariate lognormal distribution was employed to describe the joint distribution of concentration (C) and rainfall amount (R) for each site. Ranges of geometric mean (μD) of biweekly deposition (D = C. R) for each site were 0.54–2.90 meq m−2 for nss-SU42−, and 0.21–1.36 meq m−22 for NO3−; that of biweekly rainfall amount (μR) was 24.1–78.0 mm. Urban or industrialized areas had high values of μD for these ions. Ranges of estimates of the slope of the regression equation of log(D/μD) on log(R/μR), were 0.45–0.99 for nss-SO42−, and 0.35–0.86 for NO3−; thus estimates of the slope for nss-SO42− tend to be larger than those for NO3−. The present analysis, consequently, statistically clarified some differences between the two ions in deposition processes which is understood in the light of current knowledge of atmospheric chemistry.

Satellite Analysis of Volcanic Clouds and Transport of Acidic Substances from Mt. Aso and Mt. Sakurajima

The satellite images of volcanic clouds in Kyushu, Japan during September–November 1989 were studied in connection with the mountain site measurement of atmospheric qualities at Unzen-Nodake and the SO2 concentration data at Aso Volcano Museum. The images strongly indicate that many high concentration events of SO2 were the results of the long-range transport of volcanic gas from Mt. Aso and Mt. Sakurajima to these stations. Brief comments on the 2000 eruption of Miyake-jima volcano are added.

Automatically Determined pH of Precipitation Samples, Collected by an Automatic Rain-Sensing Sampler and Its Spatial Distribution

Precipitation pH was automatically measured on site for each 0.5 mm-rainfall sample at 29 nationwide stations in Japan in Phase-II of Acid Deposition Survey from 1989 FY to 1992 FY by Japan Environment Agency. The mean pH of all of the stations over the entire survey period was pH 4.6. There was no pH record less than pH 3.0 which was supposed to affect plant growth. In western Japan and in remote islands in the Sea of Japan, lower pH was observed than in the other regions. Regarding seasonal variations, pH was rather lower in winter and spring. The mean pH of initial 0.5 mm-rainfall was lower than that of the whole rainfall at many stations, although it was higher at 8 stations. The monthly means of pH based on the automatic measurements of 0.5 mm-rainfall samples were compared with those from the manual measurements of biweekly samples, showing that the automatically determined pH was lower than the manually determined one by 0.3 pH unit on average. One of the possible causes of this pH difference is solution of alkali particles in the stored samples.